invention relates to an arrangement in power transmission, especially in wheel hubs of turning wheels in a vehicle, in which power is transmitted to the hubs from a driving shaft such as a drive shaft to the driven shaft by means of a constant velocity joint having an outer section fastened to the driving shaft and an inner section fastened to the driven shaft which is rotatably supported in a wheel bracket frame surrounding the driven shaft by means of a first or outer bearing and a second or inner bearing.
Designs in which wheels that steer a vehicle, normally front wheels, also drive the vehicle are popular in cars and vans. However, these are principally used in heavier vehicles only in association with all-wheel drive systems. Constant velocity joints of various types and positionings are used in automobiles and vans. However, it has usually not been possible to use constant velocity joints in heavier vehicles for the reasons described below.
In heavy vehicles it has been possible to use double cardan joints in association with beam-type axle systems.
An axle system with both steering and driving functions must, among other factors, meet the following requirements. Because of lateral and longitudinal forces being applied to the wheel, the bearing distance of the wheel bearings must be sufficiently large, in practice at least 15% of the tire diameter. The bearings must also be located centrally with respect to the width of the tire. Because of the lateral and longitudinal forces, the intersectional point of continuation of the steering axis of the wheel and the road surface must be located approximately in a center plane of the tire. In other words, the maximum distance of this intersectional point from a center plane of the tire must be less than 15% of the width of the tire. Because the change of the length of the drive shaft when the wheel is turned has to be limited, the center point of the constant velocity joint or some other power transmission joint must be approximately located at the wheel turning axis.
As stated above, several different solutions are known in association with cars and vans, in which the power is transmitted from the driving shaft to the turning wheel by means of a constant velocity joint. The most common sign in cars and vans is such that the fastening of the turning wheel and the brake disc, the wheel bearings, and an outer section of the constant velocity joint are located one after another. This type of arrangement has previously been described, for instance, in the publication Lagerungen der Vorderrader frontgetriebener Personenkraftwagen, FAG Kugelfischer, Publication No. 05115 DA.
A reversed arrangement is described in DE Publication 2,548,722 corresponding to U.S. Pat. No. 4,094,376. In this arrangement, the outer section of the constant velocity joint is fastened to the driving shaft, and the inner section to the wheel hub. In this system, the constant velocity joint and the wheel bearings are also arranged one after the other, which makes the design extremely long over the axial direction. It has also not been possible to take advantage of the space between the wheel bearings in the arrangement in accordance with this DE Publication.
If the wheel bearings and the constant velocity joints are positioned in a fashion known from the above-noted publications, it is necessary to move the center point of the constant velocity joint very far away from the center plane of the tire which, in heavy vehicles, is caused by the wide bearing distance of the bearing system and by the large size of the constant velocity joint. Therefore, with this arrangement, it is not possible to meet the requirements described above, namely that the center point of the constant velocity joint should approximately be located on the wheel turning axis. This is due to the fact that the lateral inclination of the wheel turning axis (king pin angle, KPA) must not be too high. A lateral inclination of approximately 3.degree. to 10.degree.is generally considered to be acceptable.
An arrangement is known from DE Publication 2 903 231, in which inner rings of the wheel bearings are so connected to be a fixed part of the wheel hub, and the diameter of the bearing has been made sufficiently large in order to be able to fasten the entire outer section of the constant velocity joint within the bearing system. However, in heavier vehicles this kind of arrangement is not practical, as it leads to very large-diameter bearings, for instance on the order of 300 mm. Another drawback of constructional arrangements described above, is the fact that it has become customary to use specially designed, angular-contact ball bearings of relatively low bearing capacities in such constructional arrangements.
Similar arrangements are also described in U.S. Pat. Nos. 4,119,167 and 4,273,460, in GB patent application No. 2,155,414 and in SE Publication No. 437,491. In all of these arrangements, the wheel bearings and the constant velocity joints are positioned, one after another, which makes the designs extremely long in the axial direction. These references have also failed to take advantage of the space between the wheel bearings.